Luminaire with lamp temperature control

ABSTRACT

957,921. Electric discharge lamps. GENERAL ELECTRIC CO. Nov. 24, 1961 [Dec. 27, 1960], No. 42095/61. Heading H1D. [Also in Division F4] An illuminating device comprises an enclosure having a transparent wall and means for holding in the enclosure a lamp containing a vaporizable substance, the temperature of the lamp being controlled by a heat-conducting device which extends from the interior of the lamp to the exterior, and is so arranged that its inner end contacts for heat conduction a restricted area of the lamp and its projection extending outside of the enclosure serves for heat dissipation. In one form, a part 5 of a lamp 3 is contacted by a tubular container 4 which extends upwardly to the outside of the enclosure 1 and which contains a vaporizable liquid and a non-condensable gas, and in operation, the liquid is co-operated, the vapour condensed in a copper condenser 9 and the liquid returned to the lower part of the device. Alternatively, two hollow tubes may be used, one inside the other, and the vapour forced up the inside of the smaller tube to be condensed on a heat-dissipating surface preferably cooled with cooling fins, and the condensed liquid returned between the two tubes. In either case, the outside tube may be lagged with material 20, and a heat-conducting grease used between the lamp and the heat-conducting device. Specifications 472,307 and 821,321 are referred to.

July 21, 1964 J. A. TOLBERT LUMINAIRE WITH LAMP TEMPERATURE CONTROLFiled Dec. 27. 1960 lnven tor: Joseph A.TOLbeT"G' b9 a-flfi fi His A tbo neg United States Patent "ice 3,141,621 LUMINAIRE WITH LAMPTEMPERATURE CONTROL Joseph A. Tolhert, Hendersonville, N.C., assignor toGeneral Electric Company, a corporation of New York Filed Dec. 27, 1960,Ser. No. 78,521 14 Claims. (Cl. Mil-51.11)

This invention relates generally to lighting equipment utilizingelectric discharge lamps containing a vaporizable and readilycondensable ionizing medium, and more particularly to means forstabilizing the operation of such lamps by the use of temperaturecontrol means for regulating the vapor pressure.

The power consumption of a vapor lamp and its illuminating output arevariables dependent in part upon the operating temperature of the lamp.Generally, one temperature exists at which it may be preferable tooperate the lamp. As is well known in the art, and more fully describedin US. Patent No. 2,122,285, the performance of a vapor lamp isdependent upon the coldest spot of the lamp wall. The task of keeping avapor lamp, such asthe well-known fluorescent lamp, operating at peakefliciency can therefore be reduced to one of maintaining this cold spotat a desired temperature.

One solution which has been proposed to give this result is toincorporate, as part of the lamp structure, a temperature controllingdevice such as that disclosed in the aforementioned patent. This device,while operable in an open housing such as that illustrated in thatpatent, if put in an enclosure such as a luminaire will quickly lose itscooling potential since heat dissipation by the device is limited. As aresult, many contemporary luminaire designs incorporate fans and thelike to insure adequate cooling of the lamps.

It is therefore an object of this invention to provide a temperaturecontrol system for an enclosed lamp.

It is also an object of this invention to provide a temperature controlsystem for enclosed lamps wherein the lamp may be changed withoutchanging the control system.

It is a further object of this invention to provide a temperaturecontrol system for an enclosed lamp which will be operable over a widerange of ambient temperatures.

It is a further object of this invention to provide a temperaturecontrol system for an enclosed lamp which requires no power to operate.

It is a further object of this invention to provide a temperaturecontrol system for an enclosed lamp which has high reliability in thatno mechanical moving parts are employed.

Briefly stated, in carrying out the invention in one form which may bepreferred, a fluorescent lamp is removably secured in an enclosurehaving a transparent wall. A temperature controlling device is providedwhich includes a container having a liquid refrigerant and anon-condensable gas therein. A portion of the temperature controllingdevice is positioned to removably contact some point on the lamp walland transfer heat to the refrigerant from this point. The containerincludes a portion positioned outside the enclosure so as to be cooledby the atmosphere and cause condensation of any refrigerant which hasbeen vaporized.

The invention will be better understood from the following descriptiontaken in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic cross-section of a fluorescent street-lightingluminaire incorporating a temperature control system according to theinvention;

FIGURE 2 is a schematic cross-section of a fluorescent luminaireincorporating an alternative embodiment of a 3,141,621 Patented July 21,1964 temperature control system according to the invention; and

FIGURE 3 is a schematic enlarged detail of a portion of the temperaturecontrol system shown in FIGURE 2.

Referring now to FIGURE 1, an enclosure is shown consisting of a sheetmetal hood element 1 and a globe or transparent wall 2 which may be madeof an acrylic resin. Removably secured in the enclosure is a tubularfluorescent lamp 3 (shown in cross-section) which is supported bysuitable supporting means not shown. The lamp may be of the typedescribed and claimed in Patent 2,915,664, wherein its elongatedenvelope is indented or grooved along its length giving it akidney-shaped crosssection thereat.

In accordance with the invention, a heat conducting rod 4 is provided,which may be of copper or any other good heat conducting material, andwhich is positioned so as to have one end preferably notched at 4' andremovably contacting the lamp 3 at the area 5 which may be midway of thelength of the lamp. The conducting rod 4 extends into and is joined to atubular metal evaporator 6, preferably of stainless steel. The inner end5' of the rod 4- is serrated to promote boiling of a refrigerant inevaporator 6. Extending upwardly from the evaporator 6 is a conduit 7,of stairdess steel for example, which passes through an aperture 8 inthe hood wall to connect with a condenser 9, here illustrated as ahemispherical chamber of copper and which may be secured to the exteriorof the hood 1 by suitable brackets with interposed thermal insulationindicated at 9'. In order to limit the heat transferred to the controlsystem from the interior of the luminaire to that transferred from thelamp 3 to the evaporator 6, particularly from the area 5 of the lamp atwhich the conducting rod 4 makes contact, a suitable heat insulatingsubstance, which may be a polyester or urethane foam insulationgenerally indicated at 20, is provided to enclose the remaining portionsof the rod 4, the boiler 6, and the conduit 7, which are contained inthe enclosure formed by the hood 1 and the transparent Wall 2.

As is Well known to those skilled in the art, a reflector 21 may beprovided to direct light from the lamp 3 in a desired manner. Theconducting rod 4 and the insulation 26, which surrounds this rod, extendthrough an aperture 22 in the reflector 21. All joints between parts ofthe cooling device are preferably silver soldered to form a hermeticallysealed system.

In order to prevent deterioration of the parts within the enclosure bythe effects of the atmosphere, it is usually preferable to provide agasket 23 at the junction of the hood 1 and the transparent wall 2. Forthe same reason, a sealing washer 24- may be provided around the conduit7 to seal the aperture 8 in the wall of the hood 1.

To facilitate the transfer of heat between the lamp 3 and the conductingrod 4, a suitable biasing means such as the spring 25 may be provided.The spring 25 may be attached to the lamp 3 by means of a clip 19 whichmay be removed when the lamp is to be changed. The heat transfer is alsoimproved, in the operation of a lamp cooled in accordance with theinvention, by applying a grease with high heat conductivity at the area5 between the rod 4 and the lamp 3. A suitable grease for this purposehas been found to be the product manufactured by Iohns-Manville underthe trademark Nodrseal-type HK.

As will be evident from FIGURE 1 of the drawings, a second lamp, notshown, may be provided within the enclosure formed by the hood 1 and thetransparent wall 2 on the left side of this enclosure as viewed in thisfigure. When this is done, a temperature control device similar to thatalready described is provided and it exv 3 tends upwardly to the righ.Of course, the luminaire may be designed to accommodate more than twolamps.

The lamp 3 may contain a quantity of a vaporizable substance such asmercury, and as is well known to those skilled in the art, a smallamount of a gas such as argon which facilitates starting of the lamp.The vapor pressure of this vaporizable substance is dependent upon thetemperature of the coldest spot or area of the lamp wall. In theilluminating device of FIGURE 1, this spot becomes the area 5 throughthe effects of the temperature control system of the invention.

A quantity of a liquid refrigerant is placed in the container formed bythe evaporator 6, the conduit 7 and the condenser 9, together with anon-condensable gas, that is, a gas which has a boiling point far belownormal ambient conditions, which will not become dissolved in therefrigerant. By selection of a suitable refrigerant and by filling thecontainer with a gas at the proper pressure, the boiling temperature ofthe refrigerant can be controlled. For example, a temperature of 100 F.can be obtained as the boiling temperature. As the lamp 3 tends to riseto a temperature higher than 100 F., the refrigerant in the boiler 6will become heated to its boiling point and begin to vaporize. Thevaporizing of the refrigerant absorbs heat transferred from the lamp 3along the rod 4 thereby cooling the area 5 on the lamp 3 to atemperature near the desired temperature. The refrigerant vapors risefrom the boiler along through the conduit 7 to the condenser 9 which maybe provided with fins (not shown) to facilitate the transfer of heat tothe ambient air. By this transfer of heat to the ambient air, the wallsof the condenser 9 become relatively cool and the refrigerant willtherefore condense. The condensed refrigerant will flow back down theconduit 7 to the evaporator 6 where it once again may be boiled.

The liquid refrigerant in evaporator 6 may suitably consist of, forexample, methylene chloride or one of a group of fiuorochloromethanesand ethanes available under the trademark Freon, preferably thatdesignated Freon 11 and consisting of Trichloromonofluoromethane (CClF). The noncondensable filling gas in the container may suitably consistof a gas such as nitrogen, helium, etc.

The cooling system may be charged, for example, with 2 cc. of Freon 11at atmospheric pressure and 0 F. temperature, and with helium gas atatmospheric pressure and room temperature. The evaporator 6 isproportioned to hold the entire charge of refrigerant, and it ispreferably enlarged in diameter, as shown, so that a minimum liquidheight is available for heat conduction up the tube 7. On the otherhand, the tube 7 is preferably minimized as to diameter and wallthickness so that heat conduction to the exterior under low ambientconditions does not result in excessive cooling of the wall of the lamp3.

It was previously mentioned that there is a temperature at which afluorescent lamp will operate most efiiciently, and it is well knownthat the illuminating efficiency of a fluorescent lamp will drop offsharply at temperatures below the desired temperature and less sharplyat higher temperatures. It is relatively easy to keep a lamp hot enoughdespite a cold ambient temperature merely by placing the lamp in anenclosure, since the heat generated by the lamp tends to be retained inthe enclosure. The problem of controlling the lamp temperature isreduced therefore to one of maintaining the cold spot of the lamp at thedesired temperature.

By the temperature controlling system of this invention, the cold spotof the lamp can be maintained at the desired temperature as long as theambient temperature remains somewhat less than this desired temperature.With the temperature controlling system of this invention, therefore, ifthe selected operating temperature of the lamp is made high enough, thelamp can be made to operate at this temperature regardless of variationsin the ambient temperature.

Referring now to FIGURES 2 and 3 of the drawing, an alternativeembodiment of the invention will be described. An enclosure is showncomprising a hood 1 and a transparent wall 2 in which is removablysupported a lamp 3 in a manner similar to that described in connectionwith FIGURE 1. A heat-conducting rod 26 is positioned so as to have aportion near one end removably positioned in good heat-conductingrelationship with a selected area of the lamp 3. The other end of theheat-conducting rod 26 extends into a con- 7 tainer 27 which may beformed from thin-walled metal tubing. Substantially concentric with thecontainer 27 is a small tube 28 which is supported within the container27 so as to provide inner and outer chambers. The container 27 extendsupwardly from its connection with the heat-conducting rod 26, through anaperture 29 in the hood member 1, and is preferably provided withcooling fins 27' at its outer end. A sealing Washer 30 is providedaround the container 27 so as to seal the aperture 29 in the wall of thehood 1. That portion of the container 27 which is located outside theenclosure formed by the hood 1 and the transparent wall 2 functions as acondenser 31. In a similar manner to the embodiment of FIGURE 1, asuitable heat insulating substance generally indicated at 20 is providedto enclose the remaining portions of the rod 26 and the container 27which are contained Within the enclosure.

Referring to FIGURE 3, the bottom of the inner tube 28 is shown as beingjoined to the container 27 at the area 33 where the heat-conducting rod26 enters the container 27. One or more apertures 34 are provided in thewall of the inner tube 28 near the bottom end of this tube. A quantityof a liquid refrigerant 35 is placed in the container 27 and by means ofthe aperture 34 fills the lower end of the inner tube 28 so as to coverthe portion of the heat-conducting rod 26 extending into this tube. Inorder to cause boiling of the refrigerant at a point in the inner tube23 above the aperture 34, a heatinsulating glass sleeve 36 may be placedabout the portions of the heat-conducting rod 26 which are positionedadjacent to the aperture 34. That portion of the inner tube whichencloses the uninsulated portions of the heatconducting rod 26 thereforefunctions as a boiler.

In operation, this embodiment of the invention functions in a similarmanner to a coffee percolator. When the end 37 of the heat-conductingrod 26 reaches the boiling point of the liquid refrigerant 35, theliquid refrigerant boils, forcing drops of the refrigerant up the innertube 28. These drops, and the vaporized refrigerant rise to the upperend of the inner tube 28 and emerge from the open top 38 of this innertube to flow against and be cooled by the walls of the condenser portion31 of the container 27. The cooled refrigerant then flows down theinside of the container 27 to the bottom where it may pass back into theinner tube 28 by means of the aperture 34.

While a particular embodiment of a temperature controlling device for afluorescent lamp employing this invention has been shown and described,it will be obvious that changes and modifications can be made withoutdeparting from the spirit of the invention and the scope of the appendedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

. 1. An illuminating device comprising an enclosure having a transparentwall, a lamp containing a vaporizable substance removably mounted insaid enclosure, a temperature controlling device for said lamp, saiddevice including a container having a first portion removably contactingin heat-conducting relation a selected area of said lamp within saidenclosure, said container also having a second portion positionedoutside said enclosure, and a vaporizable liquid and a non-condensablegas in said container.

2. The illuminating device defined in claim 1 wherein said containerincludes a conduit upwardly extending from said first portion to saidsecond portion.

3. The illuminating device defined in claim 1 wherein a heat-insulatingsubstance encloses the portions of said container within said enclosure.

4. An illuminating device comprising an enclosure having a transparentwall, a lamp containing a vaporizable substance removably mounted insaid enclosure, a temperature controlling device for said lamp, saiddevice including a heat-conducting rod having a first portion removablycontacting in heat-conducting relation a selected area of said lampwithin said enclosure, a container having a first portion inheat-conducting relation to said rod within said enclosure, saidcontainer also having a second portion positioned outside saidenclosure, and a vaporizable liquid and a non-condensable gas in saidcontainer.

5. An illuminating device comprising an enclosure having a transparentwall, a lamp containing a vaporizable substance removably mounted insaid enclosure, a temperature controlling device for said lamp, saiddevice including a heat-conducting rod having a first portion removablycontacting in heat-conducting relation a selected area of said lampwithin said enclosure, a container comprising an evaporator section inheat-conducting relation to said rod, a condenser section positionedoutside said enclosure, a conduit connecting said evaporator andcondenser sections, said conduit extending upwardly from said evaporatorsection to said condenser section, and a vaporizable liquid andnon-condensable gas in said container.

6. An illuminating device as defined in claim 5 wherein aheat-insulating substance encloses the portions of said container withinsaid enclosure.

7. An illuminating device as defined in claim 6 further includingreleasable biasing means for biasing said first portion of saidheat-conducting rod and said selected area of said lamp together.

8. An illuminating device as defined in claim 7 further including aheat-conducting grease between said first portion of saidheat-conducting rod and said selected area of said lamp.

9. An illuminating device comprising an enclosure having a transparentwall, a lamp containing a vaporizable substance removably mounted insaid enclosure, a temperature controlling device for said lamp, saiddevice including a heat-conducting rod having a first portion removablybiased against said lamp, a container comprising a boiler section inheat-conducting relation to said rod, a condenser section positionedoutside said enclosure, a conduit connecting said boiler and condensersection, said conduit extending upwardly from said boiler section tosaid condenser section, and a quantity of liquid refrigerant and anon-condensable gas in said container.

10. An illuminating device comprising an enclosure having a transparentwall, a lamp containing a vaporizable substance removably mounted insaid enclosure, a temperature controlling device for said lamp, saiddevice including a heat-conducting rod having a first portion removablybiased against said lamp, an elongated tube having positioned in thebottom end thereof a second portion of said heat-conducting rod, saidtube further having at least one aperture adjacent to said secondportion of said heat-conducting rod, an elongated container enclosingsaid tube and sealed to said tube at the bottom so as to provide achamber outside said tube, said elongated container having a condenserportion extending outside said enclosure, and a vaporizable liquid andnon-condensable gas in said container.

11. The illuminating device defined in claim 10 wherein said secondportion of said heat-conducting rod is enclosed in an insulating sleeveextending from the bottom of said elongated tube past said aperture.

12. The illuminating device defined in claim 11 where in saidvaporizable liquid is a liquid refrigerant.

13. The illuminating device defined in claim 12 wherein aheat-insulating substance encloses the portions of said elongatedcontainer within said enclosure.

14. A luminaire comprising a hood having a transparent globe sealedthereto defining an enclosure, a lamp containing a vaporizable substanceremovably mounted in said enclosure, a reflector for directing lightfrom the lamp through the globe mounted within said enclosure, and meansfor controlling the temperature of a selected area of the lamp, saidmeans including a heat conducting rod having a first portion removablybiased against the selected area of said lamp and a second portionextending through said reflector, an elongated conduit mounted betweensaid reflector and said hood having positioned in a container portionthereof said second portion of said heat conducting rod, said elongatedconduit having a condenser portion extending outside said hood, and avaporizable liquid and non-condensable gas in said container.

References Cited in the file of this patent UNITED STATES PATENTS1,188,774 Hewitt June 27, 1916 1,917,703 Daumann July 11, 1933 2,300,892Harada Nov. 3, 1942

1. AN ILLUMINATING DEVICE COMPRISING AN ENCLOSURE HAVING A TRANSPARENTWALL, A LAMP CONTAINING A VAPORIZABLE SUBSTANCE REMOVABLY MOUNTED INSAID ENCLOSURE, A TEMPERATURE CONTROLLING DEVICE FOR SAID LAMP, SAIDDEVICE INCLUDING A CONTAINER HAVING A FIRST PORTION REMOVABLY CONTACTINGIN HEAT-CONDUCTING RELATION A SELECTED AREA OF SAID LAMP WITHIN SAIDENCLOSURE, SAID CONTAINER ALSO HAVING A SECOND PORTION POSITIONEDOUTSIDE SAID ENCLOSURE, AND A VAPORIZABLE LIQUID AND A NON-CONDENSABLEGAS IN SAID CONTAINER.